I've had a couple normally law abiding friends get arrested on warrants that they've had for years without knowing. It would be a traffic ticket from long ago that they either forgot about or their was a mix up in payment. Given time that ticket slowly turns into a warrant and eventually an embarrassing arrest.
A friend from Texas discovered this whilst on a road trip, when he arrived at the Canadian border. He had to turn around and drive home, because of an bounced cheque from ~a year beforehand - that he'd never heard anything about since paying it.
